The use of disilane in the microelectronics industry to deposit semi-conducting amorphous silicon has very considerable advantages, i.e. increasing the deposition rates and reducing the deposition temperature. These advantages may be considerable, but they come up against the excessively high cost of disilane (10 times higher than that of monosilane).
Disilane is prepared at present with low yields by the chemical reaction of metal silicides with inorganic acids, or of hexachlorosilane with aluminium and lithium hydride.
Commercially available disilane is not only expensive, but is also often contaminated by impurities, such as chlorosilanes, siloxanes and hydrocarbon compounds.
A process for producing disilane from monosilane using a glow discharge and carried out at a very low pressure is also known from U.S. Pat. No. 4,568,437. However, the disilane yield obtained is only average (approximately 40% at best) and the fact that it is necessary to work in vacuo makes it difficult for a process of this kind to be used on an industrial scale.
It would therefore by very useful to have a process for producing disilane which gives good disilane yields free of troublesome impurities and is economical to carry out.